Stitched LGA connector

ABSTRACT

A land grid array connector is formed by attaching a reinforcing member to a frame and coating the reinforcing member with an elastomeric compound to form a reinforced, flexible body portion of the connector. Conductive wires are inserted in pairs in an array in the fabric extent. Free ends of the wires extend past the elastomeric compound to provide contacts of the connector. The pairs of wires provide redundancy for the contacts to ensure a reliable connection.

BACKGROUND OF THE INVENTION

The present invention relates generally to pressure contact connectors,and more particularly to a land grid array (“LGA”) connector that uses aplurality of wires as contacts that are held in a flexible body portionof the connector.

The electronics industry has seen a large growth in the past few yearsof reduced size electronic devices and appliances, such as laptopcomputers and the like. The industry is always seeking to reduce thesize of these components and to increase their functionality andcapability. Both aims are accomplished by increasing the density ofcircuits on components of the device. Although the number of circuitsestablished on a chip or circuit board may be increased, care must betaken to ensure that a reliable interconnection is established betweenthe high density component and another component of the device.

These high-density interconnections are used for microprocessor, ASICand other types of chips and may also be used to provide a connectorbetween two circuit boards. Ball Grid Array (“BGA”) packages have beenused as high-density interconnections for these type applications. InBGA style packages, pads are formed in a substrate and small, sphericalballs of solder are placed in contact with the pads. These balls arethen heated to provide connections between the chip and another circuitboard. However, these balls often exhibit poor circuit board complianceand mechanical properties in effecting contact between the chip and theopposing circuit board. They are not always suitable to overcomevariations that may occur in the substrate printed circuit board.Additionally, once the balls are heated to provide solder connections,the chip cannot be easily removed to correct any defect in thesoldering, without reworking all of the solder balls and reflowing theball grid array to the printed circuit board in another attempt toprovide a reliable connection. Thus, it can be appreciated that the useof a BGA solder package does not provide a separable device interface.

Land grid array (LGA) connectors have been developed for suchapplications and they provide circuit paths between the device and thecircuit board involving the use of conductive leads, such as formedmetal contacts, that are typically embedded in a rigid plastic substrateto connect lands, or pads on a printed circuit board to the solderballs, or lands, that may be formed on a chip or other device. Theselands are formed in a particular pattern in opposition to the solderballs/lands of the component to which the connector is mated. These LGAconnectors offer numerous advantages over BGA devices in that theyprovide to the circuit or system designer, a separable interface betweenthe chip/chip package and a circuit board that BGA devices cannotprovide because they are soldered to circuit boards to effect theirconnections. However, in LGA connectors, each conductive lead must exerta particular spring force that should be maintained in order toestablish a reliable interconnection to a device. A clamping force mustbe exerted against a chip to retain it in contact with the connector.Chips having contacts in excess of 1000 contacts may require a contactforce of well over a hundred pounds.

U.S. Pat. No. 4,998,885, issued Mar. 21, 1991 describes such a style ofconnector in which wires with ball-shaped end portions are embeddedwithin an elastomeric pad. However, the elastomeric pad must beprecisely scored to a controlled depth by a laser in the area betweenthe wires in order to increase the flexibility of the wires and theball-shaped end portions thereof. Cutting these lines too deep in theelastomeric pad presents a risk of weakening the elastomer that supportsthe wires and possibly create unreliable contacts, in that some of thewires may buckle and thereby not fulfill their individual resilientmating functions. This not only complicates the manufacture of, but alsoincreases the cost of manufacture of such connectors

The present invention is therefore directed to an improved LGA connectorand method of making the connector that overcomes the aforementioneddisadvantages.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to providean LGA connector having a flexible body portion that supports aplurality of resiliently deformable contacts arranged in a high-densitypattern so as to ensure a reliable connection between the connector andan opposing component or device.

Another object of the present invention is to provide a high density LGAconnector having a resilient body portion that is reinforced by areinforcement layer interposed between two elastomeric layers, and aplurality of contacts disposed in an array within the body portion, thecontacts having free ends that extend above opposing surfaces of thebody portion.

Another object of the present invention is to provide a reliable, highdensity LGA connector having a resilient body portion that is reinforcedby a fabric extent interposed between two elastomeric layers, and aplurality of contacts disposed in an array within the body portion, thecontacts having free ends that extend above opposing surfaces of thebody portion.

Still another object of the present invention is to provide an LGAconnector wherein the connector has a flexible body portion thatsupports a plurality of conductive wire contacts formed as flexibleloops, having free ends that extending past opposing sides of theconnector body portion.

Yet still another object of the present invention is to provide apressure-activated connector having a fabric substrate encapsulatedwithin an elastomer, the connector having a plurality of thin, resilientcontacts disposed on the fabric substrate in a predetermined array andextending through the substrate, the contacts being formed as thinfilaments of wire folded upon themselves into a dual-strand loop, thecontacts having free ends that extend on opposite sides of thesubstrate.

A still further object of the present invention is to provide a LGAconnector for high density applications, wherein the connector includesa frame that encompasses a central body portion, the body portionincluding at least one elastomeric extent that is reinforced by areinforcement member at least partially embedded therein, the connectorhaving a plurality of conductive contacts disposed in an array withinthe body portion, the contacts being formed from thin, conductive wiresthat are inserted into the central body portion, the contacts beingformed as open loops that define interconnected, redundant circuit pathsfor each contact.

Yet still another object of the present invention is to provide apressure-activated connector having a flexible body portion that issupported by a connector frame member, the frame member extending aroundthe flexible body portion and defining the perimeter of the connector,the connector having at least one recess formed therein that forms apartial receptacle for a chip or chip package, and the flexible bodyportion including an elastomeric extent presented on at least onesurface of the body portion, the elastomeric extent being reinforced bya fabric extent to which the elastomeric extent is attached, both of theelastomeric extent and the fabric extent having similar dimensions so asto impart uniform characteristics to the body portion throughout itsentire area, and the connector including a plurality of conductivecontacts that are inserted into the body portion of the connector, thecontacts including conductive wire lengths that are stitched into thebody portion, while bent upon themselves to thereby form two, adjacentand redundant circuit paths extending through the connector bodyportion, the contacts having free ends that project outwardly onopposite sides of the body portion for contacting two differentelectronic components, the contacts being supported by the body portionat approximately the mid-sections thereof.

Yet another object of the present invention is to provide a method formaking an improved LGA conductor including the steps of: forming apliable connector body portion by capturing a reinforcement memberwithin an elastomer, supporting it on a support member, passing a lengthof conductive wire through center of a hollow insertion tool, stitchingthe length of wire into the connector body portion by moving theinsertion tool into and out of penetrating contact with the bodyportion, while further cutting the wire after each such insertion so asto deposit a conductive wire in the body portion that has at least onefree end that projects above a surface of the connector body portion.

A further object of the present invention is to provide apressure-activated connector having a flexible body portion held withina rigid frame, the connector having a plurality of contacts embedded inthe body portion, the contacts being inserted in the body portion as apair of interconnected strands of conductive wire formed as open loops,each open loop having two free ends that extend past exterior, opposingsurfaces of the connector body portion, the free end portions beingangled sideways in an offset pattern matching the pattern of an opposingcircuit component, the angling of the wires increasing the contactlengths thereof and presenting a knife edge to contact pads of opposingcomponents.

Still a further object of the present invention is to provide animproved LGA connector having a flexible connector body portion formedfrom an elastomer, the body portion being supported on a frame andcontaining a plurality of individual conductive contacts, the contactsbeing formed as wire loops to provide a pair of redundant, conductivecircuit paths in the connector body portion, the body portion having aplurality of openings each of which receives a wire loop therein, thewires that form the loop extending through the body portion on oppositesides of a centerline of the opening.

The present invention accomplishes these and other objects by way of itsunique and novel structure.

In one principal aspect of the present invention and as exemplified byone embodiment thereof, the connector includes a flexible connector bodyportion that is supported in a tight outer frame. The flexible connectorbody portion utilizes a reinforcement member as a substrate, and towhich an elastomer is applied. As exemplified by a first embodiment ofthe invention, the elastomer is positioned on both surfaces of a fabricextent that is used as the reinforcement member so that it preferablyfills the interstices of the fabric to elastomer provides a self-sealingsupport surface on both sides of the fabric extent while the fabricextent provides reinforcement to the elastomer. The manner in which theelastomer attaches to the fabric extent may be an encapsulation, alamination or layering.

Conventional fabrics may be used for the fabric extent, such as thosewhich a woven in a conventional manner having warps and wefts (or fills)interlaced together, either in a uniform or staggered pattern, and it iscontemplated that even non-woven fabrics, such as felts and the like maybe used for reinforcement, provided that the elastomer used may bond orotherwise attach itself to the fabric extent in a manner to intimatelycontact the fabric extent and provide a resilient body as the connectorbody portion.

Thin wires are arranged in the connector body portion in a predeterminedarray and are inserted into the fabric substrate by passing them througha needle and inserting the needle in and out of the substrate so as to“stitch” the wire contacts in place in the connector body portion. Thewires are bent upon themselves so that a contact is formed and insertedinto the connector body portion that has the form of an open loop. Theelastomer has a consistency sufficiently resilient to grab and hold thewires as they are stitched through the connector body portion, and thefabric extent has a consistency sufficient to provide reinforcement or ameasure of rigidity to the elastomer.

In an alternate embodiment of the invention, the elastomer may beapplied to only one surface of the reinforcement member. In stillanother embodiment of the present invention, the reinforcement membermay utilize a solid sheet of film, preferably a polymer film, and mostpreferably a polyimide film such as that sold by E. I. DuPont under thetrade name “Kapton”. Such films have a desired durability and do notfray as fabrics may, and the holes for the wire contacts may be easilyformed therein by a laser to “burn” them through the entire body portionof the connector.

In another principal aspect of the present invention, the contacts areformed by stitching pairs of wires into the substrate, the pairs beingformed from single wire strands that are bent them upon themselves atone end thereof to form dual strand wire lengths, or open loops, withthe strands having a bend formed therein at one end thereof, whilehaving two ends of the wire spaced close together or adjacent oneanother at the other end of the contact, so that one free end of eachcontact preferably has a loop configuration while the other free end ofthe contact has the butt ends of two of the wire strands. The wiresextend past the substrate in a predetermined distance sufficient toprovide a plurality of resilient contact beams that flex under pressureof an opposing component, such as a chip, so that Hertzian contactoccurs between the contacts and the opposing contact pads on the circuitboard. The wires may be bent in a certain direction to define adeflection direction, rather than relying upon buckling of the wires toprovide the movement under deflection. The dual nature of the wirestrands, whether they have a circular or rectangular/squarecross-section, provide each contact of the connector with redundantcircuit paths.

In still another principal aspect of the present invention, a length ofeach wire is passed through the center of an insertion tool that takesthe form of a hollow needle, or tube, and bent upon itself to form aloop prior to the needle making an insertion stroke through theconnector body portion. The insertion tool is then withdrawn, leaving adouble strand wire held in the connector body portion at approximatelythe mid-section of the strands so that the free ends of the contactsextend past the two opposite surfaces of the connector body portion forapproximately the same length. At a preselected distance in the removalof the insertion tool, the wires are cut to form a dual strand, free endof the connector contact, so that a pair of conductive paths areestablished for each contact in a single insertion and removal stroke ofthe insertion tool, thereby providing the connector with redundancy andlower inductance.

In yet still another principal aspect of the present invention, theinsertion tool is provided with a tip being formed so that the wire mayexit from the center of the tool but from the side of the tip. This toolmay have an angled tip with a single point, or it may have multiplepoints that are aligned with each other in order to balance theinsertion force on the tool as it penetrates the elastomer and, ifpresent, its reinforcement member.

In yet another principal aspect of the present invention, a plurality ofholes may be formed in connector body such as by cutting them with alaser, or pre-punching the body portion to form the holes. Once formed,the contacts are inserted into the holes.

These and other objects, features and advantages of the presentinvention will be clearly understood through consideration of thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the following detailed description, reference will befrequently made to the accompanying drawings in which like referencenumbers refer to like parts and in which:

FIG. 1 is a perspective view of an improved LGA connector constructed inaccordance with the principles of the present invention with anelectronic component aligned with and spaced apart from a nesting recessof the connector;

FIG. 1A is an enlarged detail view of area a in FIG. 1 illustrating theexposed free ends of the wire contacts of the connector;

FIG. 2 is a perspective view of the other side (typically the “bottom”side) of the connector of FIG. 1;

FIG. 2A is an enlarged detail view of area a of FIG. 2, illustrating theother exposed free ends of the wire contacts of the connector;

FIG. 3A is a top plane view of a frame member used in the connectors ofFIG. 1;

FIG. 3B is a cross-sectioned view of a portion of the frame member ofFIG. 2A, taken along line B—B thereof;

FIG. 3C is a cross-sectioned view of a portion of the frame member ofFIG. 3A, taken along line C—C thereof;

FIG. 4 is a bottom plan view of the frame member of FIG. 3A;

FIG. 5 is a perspective view of the frame member of FIG. 3A and a fabricsubstrate in position for insertion into the frame member opening;

FIG. 6A is a top plane view of the connector frame assembly of FIG. 1,with the fabric substrate in place of the support layers molded thereto;

FIG. 6B is a cross-sectional view of a portion of the connector frameassembly of FIG. 6A, taken along line B—B thereof;

FIG. 6C is a cross-sectional view of a portion of the connector frameassembly of FIG. 6A, taken along line C—C thereof;

FIG. 6D is an enlarged detailed view of area D of FIG. 6A;

FIG. 7A is a top plane view of the connector frame assembly of FIG. 6A,but with conductive wire contacts in place thereon;

FIG. 7B is a cross-sectional view taken along line B—B of FIG. 7A,illustrating a portion of the connector and further illustrating thewire contacts in their initial orientation within the connector bodyportion and prior to bending of the wire contacts;

FIG. 7C is a cross-sectional view of the connector of FIG. 7A takenalong line C—C thereof;

FIG. 7D is a cross-sectional view of the connector of FIG. 7Aillustrating one arrangement of the wire contacts within the connectorbody portion after their bending to orient the contacts in twodirections;

FIG. 8 is a cross-sectional view of an alternate manner of mounting thefabric substrate to the connector frame;

FIG. 9 is a cross-sectional view of a portion of the connectorelastomeric substrate illustrating the fabric reinforcement thereof;

FIG. 10A is a diagrammatic sectional view of a contact stitching toolhaving a single point used in assembling the connectors with theconductive wire threaded therethrough;

FIG. 10B is a diagrammatic sectional view of the contact stitching toolof FIG. 10A after bending of the wire;

FIG. 11 is a diagrammatic view of the tool of FIG. 10, entering theconnector substrate;

FIG. 12 is a diagrammatic view illustrating how the tool of FIG. 10penetrates the flexible body of the connector and initially draws out apredetermined length of the contact wire;

FIG. 13 is a diagrammatic view illustrating the tool being removed fromits penetration through the connector flexible body;

FIG. 14 is a diagrammatic view of the tool withdrawing from near thesurface of the connector flexible body while paying out the contact wirefrom the tool into a position ready for trimming;

FIG. 15 is a diagrammatic section of a view illustrating the contactwire in place within the connector flexible body and severed from thewire supply and the insertion tool;

FIG. 16 is a diagrammatic view of a contact free end-forming memberbrought into contact with the contacts after insertion into the bodyportion; and,

FIG. 17 is a detailed view of wires used as contacts which have anon-circular cross-section;

FIG. 18 is a detailed sectional view of a portion of the connector ofFIG. 1, in place between a chip and a circuit board, illustrating themanner of conduct effected by the connector contacts;

FIG. 19A is a side view of an alternate construction of an insertiontool that may be used to insert the conductive wires into the flexiblebody portions of the connectors of the invention

FIG. 19B is a perspective view of the tip end of the insertion tool offFIG. 19A;

FIG. 19C is a detailed cross-sectional view of a portion of a connectorof the invention with the insertion tool of FIG. 19A inserted partiallytherein to;

FIG. 20 is a cross-sectional view of an alternate embodiment of aconnector constructed in accordance with the principles of the presentinvention;

FIG. 21 is a detail view, partly in section, of a body portion for usewith the connectors of the invention that has a solid reinforcementmember disposed therein;

FIG. 22 is a partial sectional view of a connector body portion in placewithin the connector and being subjected to a punching member to formopenings therein for the connector contacts;

FIG. 23 is a diagrammatic elevational view partly in section of aninsertion tool aligned with an opening in the connector body portion ofconnectors of the present invention;

FIG. 24A is a diagrammatic plan view of FIG. 23 taken along lines 24—24thereof, illustrating the orientation of parts where round wire is usedfor the connector contacts;

FIG. 24B is a diagrammatic plan view of FIG. 23 taken along lines 24—24thereof, illustrating the orientation of parts where rectangular wire isused to form the connector contacts;

FIG. 25 is a perspective view of an alternate embodiment of a wireinsertion tool that may be used in the methods of the invention;

FIG. 25A is an elevational view of the insertion tool of FIG. 25;

FIG. 26 is a perspective view of an alternate embodiment of a wireinsertion tool that may be used in the methods of the invention;

FIG. 26A is an elevational view of the insertion tool of FIG. 26;

FIG. 27 is a perspective view of a punching tool that may be used withthe methods of the invention to pre-punch, or pierce openings in theconnector body portion;

FIG. 28 is a perspective view of an alternate punching tool that may beused with methods of the invention; and,

FIG. 29 is a sectional view of another alternate embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an improved land grid array (“LGA”) connector 20constructed in accordance with the principles of the present invention.The connector 20 includes a frame member 21 that holds, or encloses, aflexible body portion 22 at the connector 20 disposed within an opening23 of the frame member 21. The body portion 22 of the connector 20 isheld within the frame member opening 23 by a plurality of sidewalls 25of the frame member 21 that surround the opening 23 in a manner suchthat a top recess 24 may be defined in the top surface of the connector20, as well as a bottom recess 27, if the particular application of theconnector warrants it.

It can be seen that the connector 20 is generally rectangular or squarein shape, although it will be understood that other configurations maybe used. The top recess 24 is adapted to receive therein a circuitcomponent, such as a chip, IC package, ASIC, microprocessor, circuitboard 26 or the like, while another similar circuit component may besimilarly received on the bottom side of the connector 20 in a lowerrecess 27. (FIG. 2.) Typically, such a component may include a circuitboard that is dimensioned to fit in the lower recess 27, although insome applications, the frame member sidewalls 25 may be formed on thelower side of the connector 20, flush with the lower surface of theconnector body portion 22, eliminating any bottom recess, so that theconnector 20 may be mounted directly to a circuit board. In order toprovide a conductive path between the two circuit components, theconnector 20 is provided with a plurality of conductive contacts 28formed as thin wires, or filaments. These contacts 28 have two free ends29, 30 that extend upwardly away from the exterior surfaces 32, 33 ofthe connector body portion 22.

The connector 20, in its application, may be mounted to a circuit boardand accordingly, may include one or more mounting holes 34 formed in theframe member 21. Portions of the frame member may be raised with respectto the remainder of the frame member to serve as standoffs 35 (FIG. 2)to slightly elevate the lower surface 33 of the connector body portion22 and provide a slight air gap between the lower surface and a circuitboard (not shown) to which the connector 20 is mounted which canfacilitate solder cleaning if the connector is used in a solderedapplication.

FIG. 3A illustrates the frame member 21 in an open state without thebody portion 22 supported therein. The frame member 21 and its sidewalls25 may be formed in a suitable manner, such as by injection molding froma plastic or other electrically insulative material. The frame member 21is preferably molded as one piece, although alternate constructions maybe utilized. In this embodiment of the invention, a fabric extent 37(FIG. 5) is used as a reinforcement member to give the body portion 22some support, and is cut to a predetermined configuration, whichpreferably matches that of a support shoulder 38 (FIG. 4) that is formedon one of the surfaces of the frame member 21. The fabric extent 37 ispreferably formed from a fabric, such as nylon or fiberglass, that ispreferably cut to size using a laser or a blanking die. Natural fabricsmay be used, but it will be noted that the use of synthetic fabrics forthe fabric extent, such as fiberglass, is beneficial in that fiberglasshas a very low coefficient of thermal expansion (approaching almost azero value) which reduces any expansion from occurring in the connectorbody portion 22 during operation, and it further has better heattransfer capabilities than conventional insulators. The use of a laserin cutting the fabric extent is beneficial in that heat generated by thelaser is able to seal the edges of the fabric and minimize any frayingthat might occur in the loose ends of the fabric after cutting.Preferably, fabrics which are woven and have interleaved threads, suchas illustrated in FIG. 9, are used, but other, non-woven fabrics, suchas knit fabrics and felts may be used. As mentioned in greater detailbelow, in some instances, the reinforcement member may include a film.

The shoulder 38 is illustrated as being formed on the bottom surface(FIGS. 3B, 3C & 4) of the frame member 21. The shoulder 38 is recessedas shown, and extends around the inner perimeter of the frame member 21.This shoulder 38 provides a means for accurately placing the fabricextent 37 in the frame member 21 and also provides a support for theelastomer that is attached to the frame member 21 and the fabric 37. Inorder to retain the fabric extent 37 in place in the shoulders 38,raised catches, or ribs 40, may be provided along the four sidesthereof, which can be used to contact the fabric and hold it taut withinthe frame member 21 so as to prevent any trampoline effect, or othertype of sagging, from occurring during subsequent processes. These ribs40 may also be used in the heat staking of the fabric extent 37 to theframe member 21. The fabric extent 32 may be placed over the framemember and brought into contact with it and heat applied to the ribs 40,causing them to melt and grip the fabric extent 37 in a manner similarto that known in the art. Although these ribs 40 are illustrated in thecenter portions of the shoulders 38, they may extend longer than shownto provide additional staking capability. When the elastomer isovermolded to the frame member, the elastomer will retain and capturethe loose ends of the fabric extent in that area.

The fabric extent 37 may also be pressed over the ribs 40 duringattachment and one of the elastomeric layers 34, typically the onesituated on the “top” face of the connector 20, may be molded to theframe member 21 opposite the shoulder 38 and ribs 40. In thisdescription, the term “top” will refer to surface of the connector thatreceives and opposes the circuit component 26. Once the fabric extent 37is placed into the frame member 21 and positioned on the shoulder 38, itis preferably permanently secured in place by overmolding, or otherwiseapplying an elastomer to opposite sides of the frame member 21 and thefabric extent 37.

In another embodiment of the invention, as illustrated in FIG. 21, thereinforcement to the body portion 22 may be provided in the form of asolid film member 337. The solid film member 337 is preferably formedfrom a polymer film, which does not fray, as may the fabricreinforcement layer at times, which may result in fabric threadsclinging to the conductive contacts and possibly affecting the integrityof the connector. Useful results have been obtained by using polyimide(polymer) films sold under the trade name “Kapton” by E. I. Dupont. Sucha reinforcement member also differs from the fabric ones discussed abovein that it does not have openings between adjacent threads through whichthe elastomer may flow during formation of the body portion 22.

In one sense of the invention, the elastomer may be considered as twoelastomeric layers 41, 42 extend along the top and bottom surfaces 32,33 of the connector body portion 22. However, it will be understood thatthe term “layer” as applied to the elastomer is intended to be given itsbroadest interpretation and hence, will include two separate layers ofelastomer or a single structure formed where the elastomer penetrates orpasses through the interstitial openings 43 defined between adjacentthreads 44 of the fabric or other reinforcement extent 37, 337 tocooperatively form a single structure thereamong. (FIG. 9.) In thismanner, where the elastomer covers all of the exposed surfaces of thereinforcement extents 37, 337, the extents 37, 337 are considered to be“encapsulated” within the elastomer, with the elastomer forming the topand bottom surface of the body portion. Alternatively, if the two layers41, 42 do not flow into each other, but nevertheless bond, or otherwiseattach, to both themselves and the fabric extent 37 as illustrated inFIG. 9, by contacting each other through the interstitial areas presentbetween adjacent threads of the fabric extent 37, the resultingconstruction may be considered to be “integrated” with the elastomer, or“sandwiched” between two elastomer layers, with the elastomer extendingalong the top and bottom surfaces of the body portion. Still further,the elastomer layers 41, 42 may be placed in intimate contact with theopposite sides of the reinforcement extents 37, 337, by subjecting allthree of these members to elevated heat and pressure to form what may beconsidered as a “laminated” construction. Still further, in someapplications, the reinforcement extents 37, 337 may be coextruded withtwo elastomer extents, or they may also be dipped in the elastomer tocoat both sides thereof with a “layer”.

In order to ensure that a proper bond between the body portion 22 (i.e.,the reinforcement extents 37, 337) and the elastomer layers 41, 42 tothe connector frame member 21, a series of anchoring cavities 46 may beformed in the frame member 21 at predetermined locations. As shown inthe drawing, these cavities 46 may communicate with the frame memberopening 23 and extend within the shoulder portion 38 formed in the faceof the connector 20. These cavities 46 preferably extend throughthickness of the frame member 21 and may include offset cavity portions51, 52 that are aligned with each other but extend in an offset mannerfrom each other so as to form an opening in the frame that extends intwo different directions, which will fill with the elastomer to therebyfirmly anchor the body portion 22 to the connector frame member 21.Examples of suitable elastomers include, but are not limited to, solidsilicones, silicone foams and rubbers, synthetic rubbers, triblockcopolymers and the like. The durometer of the elastomer also contributesto the operation of the body portion with higher durometers beingpreferred for improved retention of the wires inserted into the bodyportion openings. For example, it has been found that an elastomer witha durometer of 70 on the Shore A Scale provides better wire retentionthan one with a Shore A durometer of 40.

When so filled with the elastomer, these anchoring cavities 46 and theiroffset portions 51, 52 will engage the frame member sidewalls in twodifferent directions to provide a suitable anchoring in addition to anynatural adhesive properties the elastomer may have. The alignment ofthese offset cavity portions 51, 52 is best shown in FIGS. 3B and 6A,while the manner in which the elastomer fills them is best shown in thesectional view of FIG. 6C. These cavities 46 serve to provide a meansfor interlocking the elastomer layers 41, 42 to the frame member 21, oras anchors as to each other when the layers 41, 42 are formedsimultaneously on the frame member 21. These anchoring cavities 46 arebest filled with the elastomer is applied to the fabric extent 37 afterattachment to the frame member 21, by way of a suitable overmoldingprocess.

In an alternate anchoring and fabric-capturing construction, asillustrated in FIG. 8, the frame member 21 may have a channel, orfilling groove 100, formed therein that may extend around the entireperimeter of the connector frame opening. This channel 100 receives theends or edges 101 of the fabric extent 37 and when the elastomer isapplied to thereto, the elastomer portion on the lower side of theconnector will fill the channel 100 and force the fabric edges 101 intoit to provide a taut, but flexible body portion of the connector.

The inner edges 54 of the frame member 21 may be chamfered asillustrated in FIG. 5 at 55, so as to increase the surface area thereofto provide more area in the elastomer to contact and adhere to as it ismolded or poured into the frame opening 23. The two elastomer layers 41,42 serve to encapsulate ends of the fabric extent 37 and to cover theexposed surfaces thereof, while the fabric extent provides reinforcementto the elastomer layers 41, 42 and gives it a measure of tautness. Thefabric 37 also serves to partially support the wires inserted into thebody portion 22 and the elastomer resiliency further holds the contacts28 in place and provides a sealing action around the wires of thecontacts. It is contemplated that the fabric extent and elastomer layersmay also be separately formed, subsequently attached to each other andthen assembled into the connector frame after its forming.

The use of the elastomer and the fabric extent (or other reinforcingmember) complement each other in the use of the invention, for while theelastomer provides flexibility to the body portion of the connector, thefabric provides reinforcement and a measure of rigidity to the flexiblebody portion that supports the contacts so as to reduce the overallthickness of the connector body portion that supports the contacts, andthereby achieve the shortest possible mating height for the connector20. In this regard, it is believed that thicknesses of about 0.5 mm maybe achieved for the body portion 22 when sandwich, encapsulation andcoextrusion types of body portion construction are used wherein thefabric extent 37 has an elastomeric layer 41, 42 applied to both sidesthereof. Where the fabric used in the extent 37 has a thickness of about0.15 mm and the elastomer layers each have a similar thickness, theresulting aggregate thickness of the body portion is about 0.45 mm.

Insofar as the overall mating height of the connector 20 is concerned,it is believed that it is possible to achieve with the invention, freeends 29, 30 of the contacts 28 that project past the exterior surfaces32, 33 of the body portion 22 a distance of about 0.25 mm, thus givingan expected total body portion mating height (obtained by adding thelengths of the contact free ends 29, 30 to the thickness of the bodyportion 22) of about 0.95 mm. In such instances, the connector framemember 21 may have a thickness of only about 1.5 mm, thereby creating anextremely thin, but high-density connector that has low insertionforces. As mentioned above, it is also contemplated that the elastomer41, 42 may be applied to only one of the two surfaces of the fabricextent, or vice-versa, thereby further reducing the eventual thicknessof the mating area of the connector 20. The type of fabric may alsoinfluence the eventual thickness of the body portion. A fabric extenthaving a uniform weave will create a homogenous body portion and improvethe consistency of the body portion. A random weave fabric may be usedthat reduces the thickness of the connector body portion.

In another important aspect of the invention and as diagrammaticallyillustrated in FIGS. 10-15, the conductive contacts 28 are inserted intobody portion 22 by “stitching” them in place. The contacts 60 areinserted into the body portion 22 of the connector preferably by aprogrammable sewing machine 20 that employs a reciprocating, stitchingmotion. An extent of conductive wire 63 is incrementally fed through thecenter passage, or lumen, 62 of an insertion tool 61 prior to enteringthe body portion 22. (FIG. 10A.) The wire 63 is exited from the centerof the tool and is advanced prior to insertion, so that the elastomerlayers 41, 42 will grab the wire 63 and keep a portion (i.e., a free end30) of it projecting past the lower surface. (FIG. 11.)

Depending on the wire diameter, the backward movement of the needle maybe sufficient to bend the wire upon itself to define a free end 29 thathas a looped double strand 65 as illustrated in FIG. 1D. However, it ispreferred that this bending be performed by a wire gripping means 67disposed on the relevant side of the connector body portion 22. As shownin FIG. 10B, the bending may be performed on the wire 63 by the grippingmeans 67 prior to insertion of the tool 61 into the flexible bodyportion 22. Further movement of the insertion tool 61 (FIG. 12) throughthe body portion 22 (and the fabric layer 37 and the other elastomerlayer) while the wire 63 is advanced will cause the wire to extend pastthe opposite exterior surface 33 of the other elastomer layer 42. Oncethe preselected extent of this wire 63 is reached to form the desiredlength of contact, the insertion tool 61 is then withdrawn back throughthe body portion 22. (FIG. 23.) As the insertion tool 61 is withdrawnpast the upper elastomer layer, the wire 63 pays out from the tool sothat on this side of the connector two free strands 30 of the wire arepresented in side-by-side order. The so advanced strand is then cut by asuitable means 68 at a distance substantially equal to that of the otherstrand. (FIG. 14.) Alternatively, the wire may be advanced from the toolprior to insertion and bent alongside the tool so that it will move insynchronization with the movement of the tool.

This stitching method permits the connector 20 to be made with thecontacts on very small pitches with a low height and profile. Thecontacts 28 may be formed from either lengths of round wire 63, or asillustrated in FIG. 17, lengths of polygonal cross-section wire, such asrectangular, square, hexagonal or the like may be used with the mostnoticeable benefit being the increased electrical load that the contacts28 of the connector 20 can carry. Also, when the wire has a non-circularconfiguration, such as a rectangular cross-section of about 0.1 mm by0.25 mm, the non-circular wire will resist the tendency for theelastomer to turn the wire 90° due to the elastomer exerting an outerpressure on the wire. When rectangular wire is used, it is preferablyfolded upon itself on the major dimension of the cross-section. Aspreviously stated, the contacts 28 may be stitched into the body portion22 with a programmable sewing machine that can selectively insert thewires in a predetermined pattern. The pattern may be adjusted by way ofthe programing aspect of the sewing machine, i.e., software, rather thanadjusting the mold cavity as would be done with a conventional moldedconnector.

The reciprocal motion of the insertion tool, or needle/tube 61, and thebending of the wire creates an open-ended, dual strand conductive loopfor each contact 28, with each strand or “leg” of the wire forming anindependent circuit path between contacts on the chip 26 and the othercomponent to which the connector 20 is mounted. This dual strand, openloop contact includes two ends 29, 30 that project past the exteriorsurfaces of the flexible body portion 22. One end 29 of the contact maybe considered as the “loop” end of the contact because it contains theend where the wire 63 is bent upon itself, (typically upon a radius ininstances where the wire is round wire) while the other end 30 of thecontact may be considered as the “open” end of the contact because thetwo strands of wire terminate in free, unconnected ends. This dualstrand extent is beneficial because it not only provide redundantcircuit paths to ensure the validity of the connection provided by theconnector 20, but also reduces the inductance of the overall system inthat each of the contact's generally parallel circuit paths will reducethe inductance of the specific contact by approximately one-half ascompared to the use of only a single contact as demonstrated by theparallel inductance equation:L_(TOT)=(L₁×L₂)/(L₁+L₂). Additionally, thefree ends 29, 30 of the contacts 28 are small, but provide high contactpressure even though the connector requires only a small normal loadingforce to achieve a reliable interconnection and to provide effectiveHertzian contact with an opposing circuit component. The cut free ends30 (FIG. 18) of the contacts 28 have in effect, knife edges, formedthereon that can dig into the contact pads on opposing circuit boards orchip packages to break through any contamination or oxidation that mayform on the components. It is also contemplated that if necessary,solder balls 125, 126 may be added to one or both of the free ends 29,30 of the contacts 28 as shown in FIG. 20.

The preferred manner of insertion is shown diagrammatically in FIG. 23.Each opening formed in the connector body portion may be considered ashaving a centerline CA as shown in FIG. 23. The insertion tool has itsown centerline TA which for the most part, coincides with the centerlineWA of the wire being fed through the tool. Because the wire is bent uponitself to form a loop, the insertion tool is oriented at an offset OCfrom the opening centerline as illustrated. FIGS. 24A and 24Brespectively illustrate this offset in a sectional view as well as theplacement of the wire (both round and rectangular) and the tool withrespect to the openings of the connector body portion.

In an alternate manner of wire insertion, holes for receiving thecontacts 28 may be formed in the body portion 22 by burning them in witha laser, which will prevent loose parts or shreds of the fabric fromextending through the hole and forming debris on either surface of theconnector body portion 22 as a result of insertion. The laser will alsoreduce the amount of force required to penetrate the body portion whenthe holes are preformed in body portions that utilize a filmreinforcement member 337. Similarly, as illustrated in FIG. 22, apunching member 400 may be used to sequentially pre-punch holes 401 inthe connector body portion 402, penetrating through both the elastomerportion 403 and the reinforcing member 404. Contacts are then insertedinto the holes by the insertion tool described above.

FIG. 27 illustrates one style of punch 500 that has a conical portion501 formed on the tip of its elongated body portion 502. FIG. 28illustrates an alternate style of punch 510 where the body portion 511terminates in a knife end 512 that has a square or rectangular piercinghead 513. Either of these tools will preform suitable openings in theconnector body portion 22, with the tool 500 forming circular-typeopenings and the knife punch 510 forming slits in the connector bodyportion 22. Pre-piercing the connector body portion offers advantagessuch as reduced debris and improved wire loop straightness with apolyimide reinforcement film is used with the connector body portion.

Of importance in the present invention is the contact force aspect thatthe open loop construction of the wire contacts give to connectors thatutilize them. Not only are redundant, conductive circuit pathsestablished in each contact, but the closed ends 29 of the open loopseach have a radius occurring where the wire is bent upon itself, whichresults in a point contact P (FIG. 1A) being established between theclosed end portion 29 of the contact 28 and an opposing circuitcomponent. On the opposite side of the contact, where the contact freeend is composed of two, adjacent free ends of the wire, as shown in FIG.2A, the contact effected with an opposing circuit component will be aline contact, with the line occurring along one of the cut edges of thewires, shown in FIG. 2A as the bolded line H, especially in instanceswhere the wire cross section is either square or rectangular.

The process of making the connectors 20 may also include, as illustratedin FIG. 16, a forming tool, such as a mandrel 80 that comes down intocontact with the contact free ends 29, 30 on opposite sides of theconnector to form the free ends 29, 30 in one or two directions. Themandrel may be formed with symmetrical sides as shown and moved in anarc or similar movement along the arrow M of FIG. 16 to form the wireends in the manner shown, where pairs of adjacent contacts have theirfree ends directed away from each other. The end result of this typeforming is shown in FIGS. 1A and 2A, wherein pairs 81 of contacts 28 areformed so that they point toward each other at an angle. An alternatearrangement is illustrated in FIG. 16 where the mandrel 80 contacts thefree ends 29 of a pair 81 of contacts 28 and bends there free ends 29toward the body portion surface 33 at an angle that is less that 90degrees, but in opposite directions from each other. Yet anotherarrangement is illustrated in FIG. 18 where pairs of contacts 81 pointin the same direction.

FIGS. 19A-C illustrate another construction of an insertion tool 110that may be used in making of the connectors of the invention. Althoughthe single insertion tool shown in the drawings are suitable forinserting the contacts, at times it has been discovered that theelastomeric body portion 22 of the connector 20 tends to exert a slightforce on the angled surface of the insertion tool 61, increasing thelikelihood of the tool 61 “walking” into the elastomer and slightly offthe center of the intended insertion location in the flexible bodyportion 22. In order to alleviate the likelihood of this occurring, adual point insertion tool 110 may be used for inserting the contacts 28into the flexible body portion 22 of the connector 20.

As seen best in FIG. 19B, the tool 110 takes the form of a hollowneedle, or tube, with a central passage extending axially therein thatopens to the exterior at the tip end 112 thereof. Two points 115 areformed at the tip end 114 and are spaced apart from and aligned witheach other. Each such points 115 has a triangular configuration with twoslanted sides 116 on opposite ends of a centerline of each point 116.The passage opens up at the center of the tip end 112 although it may beslightly recessed back from the tip end 112 as shown so that the wire 63exits therefrom in the manner illustrated.

FIG. 19C illustrates the penetration of the tool 110 into an elastomerpart of the body portion 22. The “walking” tendency referred to above isnot likely to occur with this construction because the elastomer willoffer a resistance force F₁ on each angled face 116 of the tool tip end112, thereby keeping the tool 110 in line so that it may penetrate theelastomer in its designated spot, and even directly through anyreinforcement threads beneath it. These two forces are believed tocounteract each other and keep the tool 110 on its path into and throughthe elastomeric body portion and through any threads that may lie in itspath.

FIGS. 25 and 26 illustrate types of insertion tools. In FIG. 25A, it canbe seen that the tool 260 has a wedge shape in that a portion of itsbody 261 is sliced at an angle from an initial transverse cut in thebody 260 that forms a stepped surface 262 at the end of the slice. Theangled profile of the tool 260 increases the size of the opening ofinterior passage 263 of the tool.

FIGS. 26 and 26A illustrates another tool 270 that has a “bullet”-shapednose 271 formed at the tip end 272 of the tool body 270. This bulletshape is easily obtained by transversely slicing, or truncating, aconical end of the nose 271. In this manner, a sharp circular tip 275that surround the tool interior passage 276 is formed that will contactthe connector body when the insertion tool is pushed against it.

Although it is preferred that the flexible body portion 22 of theconnector 20 use a fabric reinforcement layer, the benefits of thepresent invention may also be obtained in connector structures that useonly an elastomeric extent for the flexible body portion. FIG. 20illustrates, in cross-section, a connector 200 having a rigid framemember 202 with an opening 204 that receives an elastomeric body portion206. Without any reinforcement layer, the body portion 206 is maintainedin its position within the opening 204 by way of the anchoring cavitiesdescribed above and as illustrated in FIG. 6D. The body portion 206contains a plurality of individual conductive contacts 28 that arearranged therein in a predetermined pattern, or array. Each contact 28includes at least two strands of thin wire 63 that extend above theopposite exterior surfaces 214, 215 of the body portion in a fashionsimilar to that described above.

Although much of the prior description has been focused on the use of aflexible body portion that uses an elastomeric material, the presentinvention also contemplates using its unique stitching aspect to insertcontacts in a more rigid body portion. FIG. 29 illustrates a connector500 having a housing 501 and body portion 502 supported by the housing.In some instances, the housing 501 and body portion 502 may be one andthe same component. In other instances, the body portion may be athinner portion or a film such as the Kapton film mentioned above. Holesmay be either drilled, cut, punched or burned (by a laser) in the bodyportion and conductive contacts 503 inserted therein using the stitchinginsertion process illustrated in FIGS. 10-15 and 23. In some instancesit may be necessary to secure the contacts 503 in their openings bymeans of an adhesive 504. As with the prior process, the contacts 503may be either formed from conductive wire or may be previously formedcontacts, such as stamped and formed contacts.

With the use of the “stitching” to insert the contacts, it will beappreciated that not just a single needle or insertion tool must be usedto effect the invention. The present invention contemplates the use ofan array or “gang” of needles so that multiple contact insertions may beperformed with each movement of an insertion head.

While the preferred embodiment of the invention have been shown anddescribed, it will be apparent to those skilled in the art that changesand modifications may be made therein without departing from the spiritof the invention, the scope of which is defined by the appended claims.

What is claimed is:
 1. A pressure-activated connector, comprising: a connector frame having an opening disposed within said frame; a flexible body portion disposed within said frame opening, the body portion containing a plurality of conductive contacts disposed in a predetermined array in said body portion and extending through said body portion, each contact having first and second free ends that project past respective first and second surfaces of said body portion, said body portion being formed from an elastomer which is reinforced by a reinforcing member, each of said contacts including a length of conductive wire that is bent upon itself and formed into an open loop, each open loop having opposing closed end and open end portions, the open loop closed end portion defining said contact first free end and the open loop open end portion defining said contact second free end said contacts being held within said body portion between said open loop closed and open end portions.
 2. The connector of claim 1, wherein each of said contacts is formed from a wire filament.
 3. The connector of claim 1, wherein each of said contacts is formed from a single wire strand that is bent upon itself to form a dual strand contact, said strand being bent upon itself at a radius coinciding with said contact first free end.
 4. The connector of claim 1, where said frame member has a plurality of cavities formed therein that provide passages through said frame member which are filled with portions of said elastomer to anchor body portion to said frame member.
 5. The connector of claim 4, where said frame member cavities are disposed on opposite sides of said frame member and communicate with said frame opening.
 6. The connector of claim 1, wherein said body portion extends around inner edges of said frame opening to define a recess in said connector frame for receiving an opposing component therein.
 7. The connector of claim 5, where said cavities disposed on one side of said frame member are aligned with and communicate with cavities disposed on the other side of said frame member.
 8. The connector of claim 1, wherein said contacts are inserted into said body portion by stitching.
 9. The connector of claim 1, wherein each of said contact first and second free ends extends away from said body portion respective first and second surfaces at angles thereto of less than 90 degrees.
 10. The connector of claim 1, wherein said reinforcing member includes a synthetic fabric extent.
 11. The connector of claim 10, wherein said reinforcing member includes a fiberglass fabric extent.
 12. The connector of claim 1, wherein said reinforcing member is a polymer film extent.
 13. The connector of claim 12, wherein said reinforcing member is a polyimide film extent.
 14. The connector of claim 1, wherein said frame member includes an interior shoulder portion that extends around said frame member opening, and said reinforcing member is attached to said frame member at said interior shoulder portion.
 15. The connector of claim 1, wherein said reinforcing member is a woven fabric extent and said elastomer encapsulates said fabric and extends through openings between threads of said woven fabric.
 16. The connector of claim 1, wherein said reinforcing member is embedded within said elastomer.
 17. The connector of claim 1, wherein said reinforcing member includes a fabric extent that is sandwiched between two layers of said elastomer, the elastomer layers defining first and second exterior surfaces of said body portion.
 18. The connector of claim 1, wherein said body portion is formed by coextruding said reinforcing member with said elastomer.
 19. The connector of claim 1, wherein said body portion is formed by laminating at least one elastomer layer to said reinforcing member.
 20. The connector of claim 1, wherein said first free ends of adjacent pairs of said contacts extend toward each other.
 21. The connector of claim 1, wherein said contacts are disposed in a plurality of opening in said body portion.
 22. The connector of claim 3, wherein said dual strand contacts are disposed in a plurality of openings in said body portion, each of the openings having a centerline and said dual strands being disposed on opposite sides of their corresponding opening centerlines.
 23. The connector of claim 1, wherein said body portion includes a plurality of openings formed therein having a size such that at least said flexible body portion grips exterior surfaces of said contacts.
 24. The connector of claim 1, wherein said open loop open end portions form a line for contacting a second opposing circuit component.
 25. An elastomeric connector, comprising: a flexible, elastomeric body portion having opposed top and bottom surfaces, a plurality of dual strand wire conductive contacts disposed in a predetermined array in said body portion and extending through said body portion, each contact having first and second free ends that respectively project past the top and bottom surfaces of said body portion, said body portion being formed from a reinforced elastomer, each of said contacts being formed from a single wire strand that is bent upon itself to form a dual strand contact, said strand being bent upon itself at a radius coinciding with said contact first free end to define a closed loop at said contact first free end and said strand having a length sufficient to locate two ends of said dual strand at said contact second free end.
 26. The connector of claim 25, wherein said elastomeric body portion includes a reinforcing member extending horizontally through said elastomeric body portion.
 27. The connector of claim 26, wherein said reinforcing member is embedded within said elastomer.
 28. The connector of claim 26, wherein said reinforcing member includes a fabric extent that is encapsulated by said elastomer.
 29. The connector of claim 26, wherein said elastomeric body portion includes a reinforcing member laminated to said elastomer.
 30. The connector of claim 25, wherein said dual strand contacts provide redundant circuit paths.
 31. The connector of claim 25, wherein said elastomeric body portion is formed from an elastomer having a sufficient durometer to retain said contacts in said body portion.
 32. The connector of claim 31, wherein said durometer ranges from between about 40 to about 70 on the Shore A Scale.
 33. The connector of claim 1, wherein each of said contacts is a stamped and formed contact.
 34. The connector of claim 1, wherein each of said contacts includes a solder ball attached to both of said contact first and second ends.
 35. The connector of claim 1, wherein said contacts have solder balls attached to their second ends.
 36. A pressure-activated connector, comprising: a connector frame having an opening disposed within said frame; a flexible body portion disposed within said frame opening, the body portion containing a plurality of conductive contacts disposed in a predetermined array in said body portion and extending through said body portion, each contact having first and second free ends that project past respective first and second surfaces of said body portion, said body portion being formed from an elastomer which is reinforced by a reinforcing member, said first free ends of adjacent pairs of said contacts extending toward each other.
 37. A pressure-activated connector, comprising: a connector frame member having an opening disposed therein; a flexible body portion disposed within said frame opening, the body portion containing a plurality of conductive contacts disposed in a predetermined array in said body portion and extending through said body portion, each contact having first and second free ends that project past respective first and second surfaces of said body portion, said body portion being formed from an elastomer which is reinforced by a reinforcing member, said frame member including an interior shoulder portion that extends around said frame member opening, and said reinforcing member is attached to said frame member at said interior shoulder portion. 